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Hardware Helper Library for C#

, 30 Nov 2007 CPOL
How to monitor, enable, and disable hardware devices from C#
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using HardwareHelperLib;

/*
 * HW_Lib_Test
 * ===================================================
 * Simple Win Form to Demonstrate HH Lib
 * Windows XP SP2, VS2005 C#.NET, DotNet 2.0
 * ====================================================
 * LOG:      Who?    When?       What?
 * (v)1.0.0  WJF     11/26/07    Original Implementation
 */

namespace HW_Lib_Test
{
    public partial class Form1 : Form
    {
        //Global library declared
        HH_Lib hwh = new HH_Lib();

        //Name:     Form1()
        //Inputs:   none
        //Outputs:  none
        //Remarks:  Default constructor
        public Form1()
        {
            InitializeComponent();
        }
        //Name:     Form1_Load()
        //Inputs:   object, eventArgs
        //Outputs:  none
        //Remarks:  In the form load we take an initial hardware inventroy,
        //          then hook the notifications so we can respond if any
        //          device is added or removed.
        private void Form1_Load(object sender, EventArgs e)
        {
            string[] HardwareList = hwh.GetAll();
            foreach (string s in HardwareList)
            {
                listBox1.Items.Add(s);
            }

            hwh.HookHardwareNotifications(this.Handle, true);
            label1.Text = listBox1.Items.Count.ToString() + " Devices Attached";
        }
        //Name:     Form1_FormClosing
        //Inputs:   object, eventArgs
        //Outputs:  none
        //Remarks:  Whenever the form closes we need to unregister the
        //          hardware notifier.  Failure to do so could cause
        //          the system not to release some resources.  Calling
        //          this method if you are not currently hooking the
        //          hardware events has no ill effects so better to be
        //          safe than sorry.
        private void Form1_FormClosing(object sender, FormClosingEventArgs e)
        {
            hwh.CutLooseHardwareNotifications(this.Handle);
            hwh = null;
        }
        //Name:     WndProc
        //Inputs:   Message
        //Outputs:  none
        //Remarks:  This is the override for the window message handler.  Here
        //          is where we can respond to our DEVICECHANGE message we are
        //          hooking.  If we received a hardware change notification 
        //          the method reloads our hardware list.  Otherwise, it must
        //          call the default handler so the message can be processed.
        protected override void WndProc(ref Message m)
        {
            switch (m.Msg)
            {
                case HardwareHelperLib.Native.WM_DEVICECHANGE:
                    {
                        if (m.WParam.ToInt32() == HardwareHelperLib.Native.DBT_DEVNODES_CHANGED)
                        {
                            listBox1.Items.Clear();
                            string[] HardwareList = hwh.GetAll();
                            foreach (string s in HardwareList)
                            {
                                listBox1.Items.Add(s);
                            }
                            label1.Text = listBox1.Items.Count.ToString() + " Devices Attached";
                        }
                        break;
                    }
            }
            base.WndProc(ref m);
        }
        //Name:     button1_Clck
        //Inputs:   object, eventArgs
        //Outputs:  none
        //Remarks:  We are using this button to demonstrate enabling a
        //          hardware device.  There are several things worth
        //          noting.  First, just to be safe we are disabling
        //          hardware notifcations until we are done.  The UI
        //          thread in .NET won't let the WndProc method run
        //          to my knowledge while you are in here but if you 
        //          were invoking these methods on different callers it
        //          would be worthwhile to disable the notifications
        //          during.  The call to SetDeviceState is designed 
        //          to allow you to pass in multiple devices in an
        //          array to disable, even though we are currently just
        //          doing the selected one.  Also the search is a
        //          substring search so be careful not to use something
        //          so generic that it will affect more devices than
        //          the one(s) you intended.  See the notes for the
        //          SetDeviceState method in the library for some
        //          important info.
        private void button1_Click(object sender, EventArgs e)
        {
            //Enable
            string[] devices = new string[1];
            hwh.CutLooseHardwareNotifications(this.Handle);
            devices[0]= listBox1.SelectedItem.ToString();
            hwh.SetDeviceState(devices, true);
            hwh.HookHardwareNotifications(this.Handle, true);
        }
        //Name:     button2_Clck
        //Inputs:   object, eventArgs
        //Outputs:  none
        //Remarks:  We are using this button to disable a device.
        //          See remarks above.
        private void button2_Click(object sender, EventArgs e)
        {
            //Disable
            string[] devices = new string[1];
            hwh.CutLooseHardwareNotifications(this.Handle);
            devices[0] = listBox1.SelectedItem.ToString();
            hwh.SetDeviceState(devices, false);
            hwh.HookHardwareNotifications(this.Handle, true);
        }
    }
}

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This article, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

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About the Author

wjfrancis
Software Developer (Senior)
United States United States
I began coding at the ripe old age of eleven (yep, I've always been a nerd). Back then every 8-bit computer on the market had its own flavor of BASIC burned into the EPROM and I was adept at most of them. Somewhere in my bedroom there was an actual bed, but you'd be hard pressed to find it surrounded as it was. My collection included a C64, VIC20, TRS80, APPLE II+, TI-99/4A, and even one of those silver Timex Sinclair "computers" with the chicklet keys.

Eventually I taught myself 6502 assembler, and later Pascal and C. While I spent the majority of my professional career doing a mixture of C++, C#, and dabbling in ARM Assembler, for the last year I've been focusing on JAVA and the Android Platform. While I am a Windows guy at heart lately I'm finding some love for UBUNTU as well.

When I am not at the computer I am hanging out with my 12 year old son. He just finished coding a javascript implementation of Conway's Game of Life. Oh yeah, I guess that means we were in front of the computer. Go figure!

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